Abstract: Based on the observation data of particulate matter mass concentration, radiosonde data, NECP reanalysis data and ground-based Lidar, a pollution event in Shenyang from March 13 to 15, 2021 was analyzed.The variations of PM concentration, atmospheric circulation background and aerosol vertical distribution were discussed.The results show that PM_2.5 mass concentrations peaked at 06:00-07:00 on March 13 with the values of 220.0-230.0 μg·m^-3, followed by a significant decline at 12:00 on March 15 and a significant enhancement of PM₁₀ at 15:00 with the concentrations up to 258.3 μg·m^-3.High levels of SO₂ and NO₂ appeared at about 10:00 on March 13 with the concentrations of 40.1 μg·m^-3 and 101.3 μg·m^-3, respectively.The maximum concentration of CO appeared between 16:00 and 17:00 on March 13 with the values of around 8.8 mg·m^-3.The highest levels of ozone always appeared in the afternoon with the values of 102.4-113.7 μg·m^-3 from 12:00 to 16:00 on March 13 and 14.Due to the enhancement of Mongolian cyclone during its eastward moving, the dust was transported southeast by the northwest wind.The unstable stratification appeared while the dust was flourishing in Shenyang, accompanied by significant upward movement, which was conducive to the vertical mixing and transport downstream of dust particles.The maximum aerosol extinction appeared at the height of 0.7 km with the values of around 6.0 km^-1 at 10:00 on March 15, when the surface lidar depolarization ratio significantly increased to 0.4-0.5, indicating that the dust or floating dust was dominated by non-spherical particles (coarse particles).